Automating Manufacturing Systems - Process Control and ...

plc function ref - 34.28
FFL, FFU, LFL, LFU - FiFo Load, FiFo Unload, LiFo Load, LiFo Unload
Description:
Status Bits:
A
B
FFL
FIFO LOAD
Source
FIFO
Control
Length
N7:0
N7:10
R6:0
10
Stack instructions will take integer words and store them, and then allow
later retrieval. The load instructions will store a value on the stack on a
false to true input change. The Unload instructions will remove a
value from that stack and store it in the Dest location. A Last On First
Off stack will return the last value pushed on. A First On First Off
stack will give the oldest value on the stack. If an attempt to load more
than the stack length, the values will be ignored. The instructions
available are:
FFL - FIFO stack load
FFU - FIFO stack unload
LFL - LIFO stack load
LFU - LIFO stack unload
EN
DN
ER
UL
Registers: none
Available on: Micrologix, PLC-5
Position 0
FFU
FIFO UNLOAD
FIFO N7:10
Dest
N7:11
Control R6:0
Length 10
Position 0
Enable - is on when the input to the function is on
Done - is on when the shift operation is complete
Error - indicates when an error has occurred
Unload - the unloaded value is stored in this bit